Amber glass is a natural material made from the resin of prehistoric pine trees. Amber is fairly rare, having a distinctive yellow-brown shading and softer feel than actual glass. Although the development of modern technology has made distinguishing between real and synthetic amber more difficult, various tests exist to help. When touched, amber should feel warmer than glass, and has a waxier finish. Amber is also a very hard material, and cannot be scratched with fingernails, unlike most synthetic lookalikes.